In orthodontics, an arch wire is used in conjunction with orthodontic brackets mounted to the patient's teeth to move the teeth to desired positions. The arch wire is configured to conform generally to the dental arch of the patient and is accommodated or seated within arch wire slots defined in the orthodontic brackets. The arch wire exerts forces on the orthodontic brackets which over time cause the teeth to move to their correct positions.
In orthodontic treatment, it is customary to place arch wire stops at specific locations on the arch wire to prevent displacement of the arch wire in the mesial/distal direction relative to one or more brackets. In some instances, arch wire stops will be provided to arrest movement at the free ends of the arch wire to prevent the arch wire from disengaging from the arch wire slot of the distalmost bracket and from making contact with (and possibly, irritating) the soft tissue (e.g. gums) in the patient's mouth. In other instances, stops may be used to fix the arch wire to a bracket/tooth combination to effect a particular transmission of forces to the bracket/tooth combination to achieve a particular result (e.g. to prevent migration of a tooth along the arch wire).
The arch wire stops that have been developed to date use a variety of techniques and/or structural components to limit mesial/distal displacement of the arch wire relative to a bracket. One known design employs a generally C-shaped clamp provided with an arch wire receiving slot. A closure member is pivotally connected to the clamp and can be moved between an open position to allow access to the arch wire receiving slot and a closed position wherein access to the arch wire receiving is restricted. The closure member has a variable thickness and is formed with an inner camming surface for engagement with the arch wire. When the closure member is moved to the open position, the arch wire receiving slot remains unobstructed and can receive an arch wire. When the closure member is moved to the closed position, the inner camming surface is brought to bear against the outer surface of the arch wire and creates a mechanical constriction (or narrowing) of the arch wire slot. As a result, the arch wire is retained between the inner walls of the clamp and the inner camming surface, and is discouraged from moving mesially or distally relative to a bracket by the friction forces acting on the arch wire.
Still other stops use different movable components to tightly hold the arch wire within the stop. For example, in some stops, a rotatable screw is threadingly engaged with a sleeve so as to project into the arch wire slot defined in the sleeve. As the screw is tightened, its lingual end bears against the outer surface of the arch wire trapping it within the sleeve.
The relatively small size of these types of stops and the fact that they include movable components have tended to make them difficult to handle and deploy in the field. Moreover, there have been some complaints that once mounted in the mouth these stops tend to be bulky and may irritate the patient's cheek or gum tissue as a result of their bulkiness. The design of these stops may also allow food to become trapped within the stop or between the stop and the patient's soft tissue or dentition. Additionally, these stops tend to loosen from, or slip along, the arch wire over time.
A more common approach to restricting mesial/distal displacement of an arch wire involves the use of crimpable, tubular or C-shaped, sleeves. The arch wire is inserted through the sleeve and its position is fixed relative to the arch wire by crimping the sleeve in place. Slippage problems have been encountered with these types of stops, as the arch wire tends to slide within the sleeve when forces are applied to it. To address these concerns, some sleeves have been provided with roughened or irregular inner wire-engaging surfaces to increase friction and enhance the gripping action of the sleeve. These roughened surfaces may be obtained by coating the inner wire-engaging surfaces with abrasive material or by mechanically roughening the surfaces. These modifications have tended to lessen the occurrence of slippage of the arch wire. However, handling and slippage problems remain. Threading of the arch wire through the sleeve can be challenging as the arch wire itself has a relatively small cross-sectional area and the passageway formed in the sleeve is also quite small. Once threaded on the arch wire (and prior to crimping) the sleeve can inadvertently move during crimping thus making precise positioning difficult.
In light of the foregoing, it would be advantageous to have an orthodontic gripping device or arch wire stop with enhanced gripping action to overcome the slippage problems heretofore experienced with existing arch wire stops. Preferably, such an arch wire gripping device would be relatively easy to handle and quick to attach on an arch wire.